乏燃料后处理中放射性核素的陶瓷固化体的结构与化学稳定性研究
发布时间：2018-08-16 15:59
【摘要】：军用核退役设施以及核电事业的发展产生了大量的锕系核素,如Pu、U、Am、Cm和Np。这些锕系核素具有半衰期长以及毒性大的特点,必须将其固化于稳固的基材中。由于陶瓷固化锕系核素时,核素可以作为组元与固化基材中的元素成键,所形成的固化体具有高包容性、高致密、核素浸出率低、抗辐照稳定性和热稳定性好等优点。因此,本文制备了三种新型陶瓷固化体(钙钛锆石-烧绿石人造岩固化体、独居石-磷钇矿固化体和钼钨钙矿固化体),其中钙钛锆石-烧绿石人造岩和独居石-磷钇矿固化体研究用于UOX型乏燃料后处理产生的锕系核素固化以及军用核设施退役产生的U和Pu元素固化,而钼钨钙矿研究用于UMo型乏燃料中锕系核素和99Mo元素的固化。根据类质同象原理,Ce3+和Gd3+离子用于模拟固化体中的+3价锕系核素(Pu3+, Cm3+, Am3+和Np3+),而Ce4+离子用于模拟+4价的锕系核素(Pu4+, Np4+,和U4+)(1)对于钙钛锆石-烧绿石人造岩固化体Ca1-xZr1-xCe2xTi2O7+δ (0≤ x≤ 0.4),在制备过程中,部分Ce4+离子被还原为Ce3+离子。固化体中存在三种晶型,即单斜钙钛锆石,四方钙钛矿以及立方烧绿石。随着Ce3+和Ce4+离子含量的增加,固化体中的相结构发生2M型钙钛锆石→4M型钙钛锆石→立方烧绿石的转变。当Ce3+和Ce4+离子含量相对较高时,固化体中易形成4M型钙钛锆石相。当Ce3+和Ce4+离子含量再次增加时,4M型钙钛锆石结构中的阳离子发生重排且阴离子发生相应的位移,致使其结构转变为立方烧绿石。固化体中模拟核素Ce的7天标准浸出量的数量级维持在10-6～10-7 g·m-2之间。(2)对于钙钛锆石-烧绿石人造岩固化体Ca1-xCexZrTi2-xAlxO7 (0.2≤ x≤0.8),固化体中存在三种相结构,分别为2M型钙钛锆石,立方烧绿石以及3T型钙钛锆石。随着Ce3+离子含量的增加,固化体中的相结构发生2M型钙钛锆石→立方烧绿石/3T型钙钛锆石的转变。固化体中模拟核素Ce的7天标准浸出量的数量级维持在10-5～10-6 g·m-2之间。(3)对于独居石-磷钇矿固化体Gd1-xYbxPO4 (0≤ x≤ 1),固化体中相界与烧结温度和模拟核素Gd含量有关。当烧结温度为1600℃时,陶瓷Gd0.9Yb0.1PO4的相结构由单相磷钇矿组成。独居石→磷钇矿相变的晶面极易可能发生在沿[020]轴方向的(200)晶面。固化体中模拟核素Gd和Yb元素的浸出机理属于溶解-沉淀型,且其标准浸出量在持续浸出7天后达到稳态。Gd和Yb的7天标准浸出量数量级维持在10-5～10-6 g·m-2之间,且浸出量随着固化体结构中P04四面体的畸变程度的增加而逐渐增加。(4)对于固化体Gd1-xCexPO4 (0 x 1),固化体的最佳合成温度应高于1300℃。当烧结温度为1400℃时,固化体GdPO4的相结构由独居石和亚稳相磷钇矿组成。随着Ce3+含量的增加,固化体中结构发生磷钇矿→独居石的转变,而固化体中独居石的微观形貌未发生显著的变化。固化体中模拟核素Gd和Ce的浸出机理属于溶解沉淀型,其浸出量在持续浸出7天后达到稳态,且与结构中的P04四面体的畸变程度有关(畸变程度越高,浸出量越大)。Gd和Ce的7天标准浸出量的维持在10-4～10-5g·m-2之间。(5)对于钼钨钙矿固化体Ca(1-x)(LiCe)x/2MoO4 (0≤ x≤ 1),随着Ce3+和Li+离子含量的增加,固化体的晶胞参数呈现反向增大的变化趋势,而平均晶粒尺寸呈现先增加后减小的变化趋势。对于钼钨钙矿固化体Ca(1-x)(LiGd)x/2MoO4 (0≤ x ≤ 1),结构精修得到的固化体组成与名义组成基本一致。固化体的晶胞参数随着随着Gd3+和Li+离子含量的增加而逐渐减小。对于所有钼钨钙矿固化体,其模拟核素(Ce和Gd)和Mo元素的浸出机理均属于溶解-沉淀型,标准浸出量均在持续浸出7天后达到稳态,且模拟核素(Ce和Gd)和Mo元素的7天标准浸出量的大小均与其结构中Mo4四面体的畸变程度有关,畸变程度越高,7天标准浸出量越大。
[Abstract]:Military decommissioning facilities and the development of nuclear power industry have produced a large number of actinides, such as Pu, U, Am, cm and Np. These actinides have long half-life and high toxicity, which must be solidified in a stable substrate. Therefore, three new ceramic solidifiers (zircon-pyrochlore, monazite-yttrium phosphate and molybdenum-tungsten-calcium carbide) were prepared in this paper. Jushi-yttrium phosphate rock solidified body is used for the solidification of actinides produced by the reprocessing of UOX spent fuel and U and Pu produced by the decommissioning of military nuclear facilities. Molybdenum tungsten calcium ore is used for the solidification of actinides and 99Mo elements in UMo spent fuel. According to the principle of isomorphism, Ce3+ and Gd3+ ions are used to simulate the + 3 valence in solidified body. Actinides (Pu3 +, Cm3 +, Am3 + and Np3 +), and Ce4 + ions (Pu4 +, Np4 +, and U4 +) (1) for perovskite-pyrochlore artificial rock solidified body Ca1-xZr1-xCe2xTi2O7 + delta (0 < x < 0.4), some Ce4 + ions are reduced to Ce3 + ions during the preparation process. There are three crystal forms in the solidified body, namely monoclinic perovskite zirconium. With the increase of Ce 3+ and Ce 4+ ions content, the phase structure of the solidified body changes from 2M-type perovskite to 4M-type perovskite to cubic pyrochlore. When the content of Ce 3+ and Ce 4+ ions is relatively high, 4M-type perovskite-zircon phase is easily formed in the solidified body. When 4M-type perovskite-pyrochlore is formed, the cations rearranged and the anions shifted accordingly, resulting in the transformation of its structure into cubic pyrochlore. The 7-day standard leaching amount of simulated nuclide Ce in the solidified body is maintained between 10-6 and 10-7 g.m-2. (2) For the solidified body of perovskite-pyrochlore artificial rock, Ca1-xZrTi2-xAlxO7 (0.2 < 0.2 < 0.2 < 0.2). X < 0.8), there are three phase structures in the solidified body, namely, 2M-type perovskite, cubic pyrochlore and 3T-type perovskite. With the increase of Ce3+ content, the phase structure of the solidified body changes from 2M-type perovskite to cubic pyrochlore/3T-type perovskite. The order of magnitude dimension of the 7-day standard leaching amount of the simulated nuclide Ce in the solidified body takes place. (3) For monazite-yttrium phosphate rock solidified Gd1-xYbxPO4 (0 < x < 1), the phase boundary in solidified Gd1-xYbxPO4 is related to sintering temperature and simulated nuclide Gd content. (200) planes along the [020] axis. The leaching mechanism of simulated nuclides Gd and Yb in solidified solids belongs to the dissolution-precipitation type, and their standard leaching amounts reach a steady state after 7 days of continuous leaching. The 7-day standard leaching orders of magnitude of Gd and Yb are maintained between 10-5 and 10-6 g.m-2, and the leaching amount varies with the distortion degree of P04 tetrahedron in solidified solids. (4) For the solidified Gd1-xCexPO4 (0 x 1), the optimum synthesis temperature of the solidified GdPO 4 should be higher than 1300 C. When the sintering temperature is 1400 C, the phase structure of the solidified GdPO 4 is composed of monazite and metastable phase yttrium phosphate rock. The leaching mechanism of simulated nuclides Gd and Ce in solidified solids belongs to dissolution-precipitation type. The leaching amount of simulated nuclides Gd and Ce in solidified solids reaches steady state after 7 days of continuous leaching and is related to the distortion degree of P04 tetrahedron in the structure (the higher the distortion degree, the larger the leaching amount). The standard leaching amount of Gd and Ce in 7 days is maintained at 10-10. (5) For Ca (1-x) (LiCe) x/2MoO 4 (0 < x < 1) solidified body of molybdenum-tungsten-calcium ore, the cell parameters of solidified body increase inversely with the increase of Ce 3+ and Li + ions content, while the average grain size increases first and then decreases. For Ca (1-x) (LiGd) x/2MoO 4 (0 < x) solidified body of molybdenum-tungsten-calcium ore The lattice parameters of the solidified body decrease gradually with the increase of Gd3+ and Li+ ions. For all the solidified bodies, the leaching mechanism of simulated nuclides (Ce and Gd) and Mo elements belongs to dissolution-precipitation type, and the standard leaching amount is continuous leaching 7. The 7-day standard leaching amount of simulated nuclides (Ce and Gd) and Mo is related to the distortion degree of Mo4 tetrahedron in the structure. The higher the distortion degree is, the larger the 7-day standard leaching amount is.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TL24;TQ174.1
，
本文编号：2186465
[Abstract]:Military decommissioning facilities and the development of nuclear power industry have produced a large number of actinides, such as Pu, U, Am, cm and Np. These actinides have long half-life and high toxicity, which must be solidified in a stable substrate. Therefore, three new ceramic solidifiers (zircon-pyrochlore, monazite-yttrium phosphate and molybdenum-tungsten-calcium carbide) were prepared in this paper. Jushi-yttrium phosphate rock solidified body is used for the solidification of actinides produced by the reprocessing of UOX spent fuel and U and Pu produced by the decommissioning of military nuclear facilities. Molybdenum tungsten calcium ore is used for the solidification of actinides and 99Mo elements in UMo spent fuel. According to the principle of isomorphism, Ce3+ and Gd3+ ions are used to simulate the + 3 valence in solidified body. Actinides (Pu3 +, Cm3 +, Am3 + and Np3 +), and Ce4 + ions (Pu4 +, Np4 +, and U4 +) (1) for perovskite-pyrochlore artificial rock solidified body Ca1-xZr1-xCe2xTi2O7 + delta (0 < x < 0.4), some Ce4 + ions are reduced to Ce3 + ions during the preparation process. There are three crystal forms in the solidified body, namely monoclinic perovskite zirconium. With the increase of Ce 3+ and Ce 4+ ions content, the phase structure of the solidified body changes from 2M-type perovskite to 4M-type perovskite to cubic pyrochlore. When the content of Ce 3+ and Ce 4+ ions is relatively high, 4M-type perovskite-zircon phase is easily formed in the solidified body. When 4M-type perovskite-pyrochlore is formed, the cations rearranged and the anions shifted accordingly, resulting in the transformation of its structure into cubic pyrochlore. The 7-day standard leaching amount of simulated nuclide Ce in the solidified body is maintained between 10-6 and 10-7 g.m-2. (2) For the solidified body of perovskite-pyrochlore artificial rock, Ca1-xZrTi2-xAlxO7 (0.2 < 0.2 < 0.2 < 0.2). X < 0.8), there are three phase structures in the solidified body, namely, 2M-type perovskite, cubic pyrochlore and 3T-type perovskite. With the increase of Ce3+ content, the phase structure of the solidified body changes from 2M-type perovskite to cubic pyrochlore/3T-type perovskite. The order of magnitude dimension of the 7-day standard leaching amount of the simulated nuclide Ce in the solidified body takes place. (3) For monazite-yttrium phosphate rock solidified Gd1-xYbxPO4 (0 < x < 1), the phase boundary in solidified Gd1-xYbxPO4 is related to sintering temperature and simulated nuclide Gd content. (200) planes along the [020] axis. The leaching mechanism of simulated nuclides Gd and Yb in solidified solids belongs to the dissolution-precipitation type, and their standard leaching amounts reach a steady state after 7 days of continuous leaching. The 7-day standard leaching orders of magnitude of Gd and Yb are maintained between 10-5 and 10-6 g.m-2, and the leaching amount varies with the distortion degree of P04 tetrahedron in solidified solids. (4) For the solidified Gd1-xCexPO4 (0 x 1), the optimum synthesis temperature of the solidified GdPO 4 should be higher than 1300 C. When the sintering temperature is 1400 C, the phase structure of the solidified GdPO 4 is composed of monazite and metastable phase yttrium phosphate rock. The leaching mechanism of simulated nuclides Gd and Ce in solidified solids belongs to dissolution-precipitation type. The leaching amount of simulated nuclides Gd and Ce in solidified solids reaches steady state after 7 days of continuous leaching and is related to the distortion degree of P04 tetrahedron in the structure (the higher the distortion degree, the larger the leaching amount). The standard leaching amount of Gd and Ce in 7 days is maintained at 10-10. (5) For Ca (1-x) (LiCe) x/2MoO 4 (0 < x < 1) solidified body of molybdenum-tungsten-calcium ore, the cell parameters of solidified body increase inversely with the increase of Ce 3+ and Li + ions content, while the average grain size increases first and then decreases. For Ca (1-x) (LiGd) x/2MoO 4 (0 < x) solidified body of molybdenum-tungsten-calcium ore The lattice parameters of the solidified body decrease gradually with the increase of Gd3+ and Li+ ions. For all the solidified bodies, the leaching mechanism of simulated nuclides (Ce and Gd) and Mo elements belongs to dissolution-precipitation type, and the standard leaching amount is continuous leaching 7. The 7-day standard leaching amount of simulated nuclides (Ce and Gd) and Mo is related to the distortion degree of Mo4 tetrahedron in the structure. The higher the distortion degree is, the larger the 7-day standard leaching amount is.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TL24;TQ174.1
，
本文编号：2186465
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